Many industrial processes rely upon a technique that can apply a uniform layer of coating material onto a discrete surface area of a moving, porous substrate. Applications include the manufacture of diapers, incontinence pads, and other hygienic products, as well as many other products. Among the various techniques, non-contact dispensers can apply a layer of coating material without physically touching the moving substrate surface. Typically, a non-contact dispenser sprays a stream of coating material from an outlet nozzle of a dispenser located adjacent to the substrate surface. Particles of coating material must cross an air gap between the outlet nozzle of the dispenser and the substrate surface.
In many industrial processes that apply a non-contact coating, the substrate moves quickly and this displaces air in and around the air gap between the dispenser and the substrate. The turbulent air flow induced by the moving substrate captures stray particles of coating material that rebound from the substrate surface. In addition, the speeding air deflects particles of coating material having low kinetic energy from the spray stream. These misdirected particles of coating material constitute airborne overspray and are transported by the turbulent air flow to various undesired locations within the production machinery.
As a consequence of the randomly misdirected overspray, maintenance personnel must periodically clean the machinery of accumulated coating material. If the buildup is not periodically removed, components may eventually become coated with enough material to create various problems in the machinery. For example, moving components of the machinery may prematurely wear, or otherwise be adversely affected, and require replacement. This decreases productivity, due to machine down-time during maintenance, and raises production costs. If the coating material is an adhesive, simple overspray collection methods, such as those used in powder coating processes, are inadequate since adhesives significantly coagulate and bind to collection heads, conduits, collection vessels and similar structures. In addition, simple overspray collection methods generate a waste stream for either disposal or recycling.
The prior art has failed to provide a suitable solution for reducing or eliminating non-contact coating overspray, especially with regard to non-contact coating of porous substrates. Thus, the coating industry continues to need an apparatus for capturing airborne particles of coating material not received or retained by the surface of the moving substrate.